The present invention relates to cigarette filters, and more particularly to cigarette filters that include vacuum deposited particulate filter material.
A variety of cigarette filters have been proposed over the years, and many of these filters include granular filter material particularly in so-called plug-space-plug filters. In these filters, spaced apart plugs, usually made of cellulose acetate, define a cavity therebetween which is filled with granulated material, such as granulated carbon, for example. The filters are attached to wrapped tobacco rods with tipping paper to produce the finished cigarettes. In many instances, the granulated material is vertically filled into the cavity during filter manufacture.
It is important that the cavity between the cellulose acetate plugs be sufficiently filled with particulate material so that tobacco smoke comes into contact with the material as it is drawn through the filter. Insufficient fill causes so-called channeling of the smoke as it passes through the cavity which results in less efficient filtering.